Now there's some pretty flawed logic.
By staggering entry, they are guaranteeing that they will be significant portion of the community.
If they let everyone in at once, there's a CHANCE things would not work, but that's what the beta stress test was for. Also, if things end up not working, then it would stop working all the same once everyone eventually gets let into the game. There's also a chance everything will run smoothly. So as a matter of fact, this option would allow them to "win".